The invention relates to a drill or milling head. In particular, this drill or milling head is suited for machines which serve to produce fine structures, such as printed circuit milling machines and engraving machines. For the purpose of changing the tool in similar types of drill or milling heads, it is known to provide a rod for actuating collet chucks which is extended through a hollow drive shaft of the motor or of the drill or milling head and engages with the collet chuck by means of gearing. In order to open the collet chuck, the actuating rod is pushed in the direction of the collet chuck, either manually by means of a hand-activated knob found above the motor or pneumatically, which causes the collet chuck to be turned, i.e. screwed, and thereby opened. However, for this the motor must first be turned off. When this is forgotten, the drill or milling head is damaged since then the actuation rod, which is not rotating, comes into contact with the collet chuck, which is rotating. Then, it can even happen that the collet chuck comes completely off the drill or milling head and thereby poses the danger of injury to people.
A drill or milling head with a rapid change mechanism is known German Patent Document from DE 34 34 699 C2. However, in this drill or milling head it also is disadvantageous that during the changing of a tool which is in place, there is at least a danger of damaging the drill or milling head if the motor accidentally was not previously switched off.